For users of different weights, an office chair may be adjusted to selectively set a restoring force acting on a backrest of the chair.
U.S. Pat. No. 8,528,973 B2 discloses a conventional adjusting mechanism used to adjust a restoring force that acts on a backrest of a chair. The adjusting mechanism has a spring element for creating the restoring force, a support, and a backrest support that is pivotably mounted about a support axis on the support. An adjusting element configured as a pair of scissors containing a first scissor arm and a second scissor arm is provided, and the scissor arms are rotatably connected to each other about a scissor axis. The first scissor arm is pivotably mounted on the backrest support about an adjusting axis. A spring force produced by the spring element acts on the second scissor arm. A first actuating lever length is defined between the support axis and the scissor axis. The lever length is changeable using an adjusting element for adjusting the restoring force by pivoting the adjusting element about the adjusting axis.
U.S. Pat. No. 9,265,348 B2 discloses a conventional adjusting mechanism serves for the weight-dependent setting of a restoring force which acts on a backrest of an office chair which is configured with a synchronous mechanism. The synchronous mechanism comprises a support, a seat support and a backrest support which are connected to one another via joint pins, the restoring force being exerted via a spring element. In order to achieve as flat a design as possible, the restoring force is transmitted with the aid of a pivotable lever via a front bearing pin to a first front joint pin, an active lever length which can be varied with the aid of an adjusting element being defined by the spacing between the bearing pin and the second front joint pin. A weight setting is made possible by the variation of the active lever length.